The Schwinger effect, a non-perturbative mechanism for particle production in strong fields, plays a crucial role in understanding quantum vacuum decay and high-energy phenomena, including heavy-ion collisions (HIC). Although holographic quantum chromodynamics (QCD) models have been widely used to study this effect, most treatments assume isotropy or consider only a single type of anisotropy, neglecting the interplay between spatial and magnetic anisotropies that arise in realistic HIC scenarios. A unified framework accounting for both anisotropies is needed to accurately model particle production. We investigate the Schwinger effect in a twice anisotropic holographic QCD model incorporating both spatial and magnetic anisotropies. Using the anti-de Sitter/conformal field theory correspondence, we compute the total potential of a particle-antiparticle pair to quantify how these anisotropies influence pair production. Our results show that the magnetic field (parameterized by $c_B$ and $q_3$ ) enhances the Schwinger effect by lowering and narrowing the potential barrier, while increasing spatial anisotropy (controlled by $\nu$ ) suppresses the process by raising and widening the barrier. These findings demonstrate that magnetic and spatial anisotropies exert competing effects on particle production, emphasizing the necessity of treating both concurrently in holographic models. This work advances the theoretical description of the Schwinger effect in anisotropic environments, with implications for understanding non-equilibrium dynamics in HIC and other strongly coupled systems.

China

Wen-Bin Chang

Defu Hou

Schwinger effect in a twice anisotropic holographic model * Defu Hou's research is supported in part by the National Key Research and Development Program of China (2022YFA1604900). Additionally, Defu Hou receives partial support from the National Natural Science Foundation of China (NSFC) (12435009, 12275104). Wen-Bin Chang is supported by the Ph.D. Research Startup Project at Hubei Minzu University (RZ2500000857)

We study electromagnetic radiation from classical sources near a planar interface separating a topological and a trivial insulator, modeled within axion electrodynamics. The system features a piecewise constant <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>θ</mi></math> term that encodes the magnetoelectric response of topological surface states. Treating this coupling perturbatively, we derive analytical corrections to the standard Liénard-Wiechert potentials and obtain modified radiation fields in the far zone. As applications, we analyze the emission from linear antennas and the bremsstrahlung radiation of accelerated charges near the interface. For antennas, the surface Hall response breaks axial symmetry and produces azimuthal modulations that grow with the electrical length, leading to distinct scaling behaviors in the total and angular radiated power. For accelerated charges, the emitted intensity is uniformly reduced by a factor <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mn>1</mn><mo>−</mo><mo stretchy="false">(</mo><msub><mi>σ</mi><mtext>Hall</mtext></msub><mo>/</mo><mn>2</mn><mi>ε</mi><mi>v</mi><msup><mo stretchy="false">)</mo><mn>2</mn></msup></math>, which we interpret as a process-specific attenuation of the radiative strength due to interference with its image magnetic monopole inside the topological medium. These results reveal how topological surface states mediate measurable modifications to classical radiation, establishing a link between axion electrodynamics, topological phases, and field theories with spatially varying couplings.

M. Ibarra-Meneses

A. Martín-Ruiz

Electromagnetic radiation mediated by topological surface states

In this paper, we systematically explore the mass spectrum of fully strange tetraquark candidates within the framework of QCD sum rules, focusing on states with quantum numbers $ J^{PC}=0^{++} $ , $ 0^{-+} $ , $ 0^{--} $ , $ 1^{--} $ , $ 1^{+-} $ , and $ 1^{++} $ . The analysis reveals the existence of fully strange tetraquark states with masses ranging from approximately $ 2.07 $ to $ 3.12 $ GeV. These predictions are compared with existing experimental observations of potential fully strange tetraquark resonances, notably the $ X(2300) $ recently reported by the BESIII Collaboration, which may be interpreted as a fully strange tetraquark state. Furthermore, the possible decay modes of these fully strange tetraquark states are analyzed, providing guidance for their identification in current and future high-energy experiments, such as BESIII, Belle II, and LHCb.

Bing-Dong Wan

Ji-Chong Yang

Fully strange tetraquark states via QCD sum rules * Supported in part by the National Natural Science Foundation of China (12575106, 12147214) and Specific Fund of Fundamental Scientific Research Operating Expenses for Undergraduate Universities in Liaoning Province (LJ212410165019)

In this study, we investigate the possibility of enhancing the di-jet resonance searches by tagging the final state radiation (FSR) jet using an event-level deep neural network. It is found that solely relying on the 4-momenta of the leading three jets allows the algorithm to achieve good discriminating power that can identify the hardest FSR jet in the signal while rejecting other soft jets. Once the invariant mass is corrected with the tagged FSR jet, the mass resolution of the signal is greatly enhanced, and the sensitivity of the search is also improved by more than 10%. By crafting the input variables carefully, the algorithm introduces minimal mass sculpting for the background, and its applicability extends to a broad mass range. This work proves that FSR jet tagging can potentially enhance di-jet resonance searches, suiting various stages of the physics programmes at the Large Hadron Collider (LHC) and High-Luminosity LHC (HL-LHC).

Bingxuan Liu

Yuxuan Shen

Yuanshunzi Sui

Enhancing di-jet resonance searches via a final-state radiation jet tagging algorithm * Bingxuan Liu is supported by Shenzhen Campus of the Sun Yat-sen University under project 74140-12255011, and by the Young Scientists Fund (C Class) of the National Natural Science Foundation of China (12405122). Both Yuxuan Shen and Yuanshunzi Sui are supported by College Students’ Innovative Entrepreneurial Training Plan Program

We investigate the collider signatures of a maximally flavor-violating $ U(1)_{L_\mu-L_\tau} $ model, where a new gauge boson $ Z^\prime $ and scalar triplets induce lepton flavor-changing interactions in the $\textit{μ}$-$\textit{τ}$ sector. Focusing on four-lepton final states at multi-TeV lepton colliders, we conduct a detailed analysis of cross sections, asymmetries, and polarization effects. We show that the signal cross section is highly sensitive to $ m_{Z^\prime} $ and the effective parameters $ \tilde{g}/m_{Z^\prime} $ , whereas it remains largely insensitive to the triplet Yukawa couplings within the phenomenologically allowed region. The forward-backward asymmetry exhibits a characteristic monotonic dependence on $ m_{Z^\prime} $ , and beam polarization can significantly suppress the Standard Model backgrounds while enhancing new physics contributions. We find that, in the phenomenologically allowed parameter space, the predicted observables remain highly sensitive to the underlying model parameters. These results show that multi-lepton final states are powerful probes of the $ U(1)_{L\mu - L_\tau} $ framework and can offer valuable guidance for future searches at muon and electron-positron colliders.

Jianing Qin

Fei Huang

Honglei Li

Zhi-Long Han

Jin Sun

Collider probes of four-lepton final states in maximally flavor-violating ${U(1)_{L_\mu-L_\tau}} $ model * Supported by National Natural Science Foundation of China (12505112, 11805081), Shandong Province Natural Science Foundation (ZR2024QA138, ZR2022MA056) and State Key Laboratory of Dark Matter Physics, University of Jinan Disciplinary Cross-Convergence Construction Project 2024 (XKJC- 202404) and Jin Sun is supported by IBS under the project code, (IBS-R018-D1)

Ground-state energy and matrix elements are reconstructed from correlators in lattice QCD by diagonalizing transfer matrix <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mover accent="true"><mi mathvariant="script">T</mi><mo stretchy="false">^</mo></mover></math> within the Krylov subspace spanned by <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mover accent="true"><mi mathvariant="script">T</mi><mo stretchy="false">^</mo></mover><mi>n</mi></msup><mo stretchy="false">|</mo><mi>χ</mi><mo stretchy="false">⟩</mo></math>, where <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mo stretchy="false">|</mo><mi>χ</mi><mo stretchy="false">⟩</mo></math> is a state generated by an interpolating field on the lattice. In numerical applications, this strategy is spoiled by statistical noise. To circumvent the problem, we introduce a low-rank approximation based on a singular-value decomposition of a matrix made of the correlators. The associated bias is eliminated by an extrapolation to the limit of vanishing variance of energy eigenvalues. The strategy is tested using a set of mock data as well as real data of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>K</mi></math> and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>D</mi><mi>s</mi></msub></math> meson correlators.

Ryutaro Tsuji

Shoji Hashimoto

Ryan Kellermann

Unbiased Krylov subspace method for the extraction of ground states from lattice correlators

We focus our attention on two-qubit mixed states as initial states, and apply the geometric measure of quantum discord to investigate quantum discord properties in the background of a Schwarzschild black hole under phase damping, phase flip and bit flip channels, respectively. Several analytical complementary relationships based on quantum discords for bipartite subsystems are proposed. For the three channel noises, the behaviors of discords are similar, the accessible discords always degrade as the Hawking acceleration rising, but sudden death never occurs, while the inaccessible discords increase from zero monotonically. Interestingly, in the case of the bit flip channel and phase flip channel, the discords perform symmetrically with the decay probability rising.

Yuxuan Xiong

Zhiling Pi

Tinggui Zhang

Xiaofen Huang

Quantum discord of mixed states under noisy channels in the curved spacetime

This study employs QCD sum rules to predict the masses and residues of spin- <math altimg='si60.svg'><mfrac><mn>3</mn><mn>2</mn></mfrac></math> doubly heavy baryons including two heavy quarks (c and/or b) and one light quark, specifically focusing on <math altimg='si1.svg'><msubsup><mstyle mathvariant='normal'><mi>&#926;</mi></mstyle><mrow><mi>c</mi><mi>c</mi></mrow><mo>*</mo></msubsup></math>, <math altimg='si25.svg'><msubsup><mstyle mathvariant='normal'><mi>&#926;</mi></mstyle><mrow><mi>b</mi><mi>c</mi></mrow><mo>*</mo></msubsup></math>, <math altimg='si34.svg'><msubsup><mstyle mathvariant='normal'><mi>&#926;</mi></mstyle><mrow><mi>b</mi><mi>b</mi></mrow><mo>*</mo></msubsup></math>, <math altimg='si42.svg'><msubsup><mstyle mathvariant='normal'><mi>&#937;</mi></mstyle><mrow><mi>c</mi><mi>c</mi></mrow><mo>*</mo></msubsup></math>, <math altimg='si52.svg'><msubsup><mstyle mathvariant='normal'><mi>&#937;</mi></mstyle><mrow><mi>b</mi><mi>c</mi></mrow><mo>*</mo></msubsup></math> and <math altimg='si57.svg'><msubsup><mstyle mathvariant='normal'><mi>&#937;</mi></mstyle><mrow><mi>b</mi><mi>b</mi></mrow><mo>*</mo></msubsup></math>. Our study provides results for the ground state (1 <italic>S</italic>), first orbital excitation (1 <italic>P</italic>), and the first radial excitation (2 <italic>S</italic>), within a consistent theoretical framework. In addition to mass spectra, we provide residue calculations as well. The calculated residues are essential for estimating the decay widths and branching ratios of these baryons at different decay channels. Our analysis incorporates nonperturbative QCD effects through operators up to dimension ten, leading to improved precision in the mass and residue calculations. These predictions offer crucial guidance for ongoing and future experimental searches, particularly in light of the current lack of empirical data for the ground and excited states, and provide a basis for comparison with future experimental data.

Iran

M. Shekari Tousi

Türkiye

K. Azizi

Doubly heavy spin- <math altimg='si60.svg'><mfrac><mn>3</mn><mn>2</mn></mfrac></math> baryons spectrum in the ground and excited states

We attempt to describe the moduli space of boundary states in the SU(2) WZW model by constructing marginally deformed solutions in open string field theory in the level truncation approximation. In contrast with other approaches to marginal deformations, our solutions exhibit a $\textit{g}$-function different from that of the background (typically lower). Thus, our method effectively combines features of both marginal and relevant deformations. After partially fixing an SU(2) symmetry of the equations of motion, we find families of solutions parameterized by the coefficient of the marginal field associated with the $\textit{J}$ current, and we identify them as Cardy boundary states with varying angle $\textit{θ}$. However, it turns out that these solutions become inconsistent once the marginal parameter exceeds a certain value, implying that they cover only a part of the moduli space. Finally, we also compare the relation between the marginal parameter and the angle $\textit{θ}$ for different solutions and we find evidence suggesting that this relation is universal for certain classes of solutions.

Czechia

Matěj Kudrna

Marginal deformations of SU(2) $\textit{k}$ WZW model boundary states in open string field theory

Matching theoretical predictions to experimental data remains a central challenge in hadron spectroscopy. In particular, the identification of new hadronic states is difficult, as exotic signals near threshold can arise from a variety of physical mechanisms. A key diagnostic in this context is the pole structure of the scattering amplitude, but different configurations can produce similar signatures. The mapping between pole configurations and line shapes is especially ambiguous near the mass threshold, where analytic control is limited. In this work, we introduce an uncertainty-aware machine learning approach for classifying pole structures in <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>S</mi></math>-matrix elements. Our method is based on an ensemble of classifier chains that provide both epistemic and aleatoric uncertainty estimates. We apply a rejection criterion based on predictive uncertainty, achieving a validation accuracy of nearly 95% while discarding only a small fraction of high-uncertainty predictions. Trained on synthetic data with known pole structures, the model generalizes to previously unseen experimental data, including enhancements associated with the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>P</mi><mrow><mi>c</mi><mover accent="true"><mi>c</mi><mo stretchy="false">¯</mo></mover></mrow></msub><mo stretchy="false">(</mo><mn>4312</mn><msup><mo stretchy="false">)</mo><mo>+</mo></msup></math> state observed by LHCb. In this, we infer a four-pole structure, representing the presence of a genuine compact pentaquark in the presence of a higher channel virtual state pole with nonvanishing width. While evaluated on this particular state, our framework is broadly applicable to other candidate hadronic states and offers a scalable tool for pole structure inference in scattering amplitudes.

Netherlands

Felix Frohnert

Philippines

Denny Lane B. Sombillo

Evert van Nieuwenburg

Germany

Patrick Emonts

Learning pole structures of hadronic states using predictive uncertainty estimation